Estimation of Tailings Dam Break Discharges
Arvind Dalpatram
USSD
Workshop on Dam Break Analysis
Applied to Tailings Dams
August 24-26, 2011
Overview
• Dam break analyses for water storage dams
•
•
•
•
Relatively simple
Lots of guidance available in literature
Often covered by regulatory guidelines
Well established numeric modelling tools/software
available
• Dam break analyses for tailings storage dams
•
•
•
•
More complex than water storage dams
Tailings more viscous than water, and not as free flowing
Not all tailings released from impoundment
Numeric modelling tools/software difficult to use or not
reliable
Overview
• Difference between water storage and tailings storage
impoundments
• Use of methodology/tools for water storage dams
Water and Tailings Storage Impoundments
Water Storage
Tailings Storage
Free Water
(supernatant pond)
Water
Dam
Tailings Beach
Tailings
(solids & water)
Dam
After Dam Breach
Tailings Storage
Water Storage
Dam
Water
Dam
Breach
Bottom
Breach
Bottom
Tailings
Tailings flow downstream of dam
Breach to Foundation Level
Tailings Storage
Water Storage
Dam
Breach
Bottom
Dam
Breach
Bottom
Tailings
All water released
Not all tailings
released
Tailings flow
downstream of dam
Volume of Tailings Released
Tailings Released
No. of
Dams
Dam
Heights
Range
Average
Lucia (1981)
11
15m to 46m
14% to 100%
40%
USCOLD (1995)
16
20m to 61m
1% to 100%
29%
Garga and Khan (1995)
19
?
3% to 100%
28%
USCOLD (1995) and
www.tailings.info
31
12m to 61m
1% to 100%
26%
M. Rico et al. (2007)
28
5m to 66m
3% to 100%
33%
Azam and Li (2010)
72
?
?
20%
Source
Outflow Volume (106 x m3)
Volume of Tailings Released (M. Rico et al.)
VF = 0.354VT1.01
Where:
VF = Outflow volume
VT = Stored volume
Impoundment Volume (106 x m3)
Source: M. Rico et al. (2007)
Steps for Tailings Dam Break Analyses
• Establish dam break scenario
• Estimate volume of tailings released
• Review flows in downstream river and potential for
transport of tailings
• Assume released tailings behave like water
• Estimate dam breach parameters
• Run numeric dam break and inundation model
• Carryout sensitivity analyses for estimated/assumed
values
Dam Break Scenarios
• “Sunny-day” Failure
• Supernatant pond at max. normal operating level
• Normal flows in river(s) downstream of the dam (e.g.,
average annual flow)
• Caused by earthquake, seepage, foundation failure, etc.
• “Rainy-day” Failure
• Flood-induced failure
• Supernatant pond at design flood level, or higher
• Flood flows in river(s) downstream of the dam (i.e., flows
most likely to occur coincident with the breach event)
• More water than sunny-day failure; more tailings
mobilized
Amount of Tailings Mobilized
• Impoundment Characteristics
• Stage/storage curve
• Shape of impoundment
• Water in the Impoundment
• Free water above the tailings
• Water retained within the tailings (i.e., water content)
• Flows in the rivers downstream of dam
Impoundment Characteristics
Tailings surface after failure
Free Water
Dam
Tailings
Tailings surface after failure
Free Water
Tailings
Dam
Water in the Impoundment and River
Sunny-day Failure
Free Water
Dam
Tailings (solids & water)
Rainy-day Failure
Water in river
Free Water
Tailings (solids & water)
Dam
Breach Parameters
• Breach Geometry
• Breach depth
• Breach width
• Breach side slopes
• Breach Formation Time
Dam Break and Inundation Modelling
• Conventional dam break and flood routing models
• Sensitivity analyses:
• Assumed tailings release volume
• Breach geometry
• Breach formation time
• etc.
References
Azam, Sahid and Li, Qiren (2010). Tailings Dam Failures: A Review of the Last One Hundred Years, Geotechnical
News, December.
Garga, V.K. and Khan, M.A. (1995). Review and Comparison of a deterministic Model for estimating Flow Out
Distance of Breached Tailings, report submitted to Resources Canada, Mining Research Laboratory.
Lucia, P.C. (1975). Review of Experiences with Flow Failures of Tailings Dams and Waste Impoundments.
Lucia, P., Duncan, J., and H.B. Seed (1981). Summary of Research on Case Histories of Flow Failures of Mine
Tailings Impoundment”, mine Waste Disposal Technology Proceedings Bureau of Mine Technology Transfer
Workshop, Denver, July 16, 2981.
Lucia, P.C. (1981). Review of Experiences with Flow Failures of Tailings Dams and waste Impoundments, PhD
dissertation, University of California, Berkeley.
Rico M., Benito G., and Diez-Herrero A. (2007). “Floods from Tailings Dam Failures”, Journal of Hazard
Management.
References
USCOLD (1995). Tailings Dam Incidents.
Vick, S. (1992). “ Inundation Risk from Tailings Dam Flow Failures, Proceedings, IX Pan-American Conference, Van
del mar, Chile, Vol. 1, pp. 1137-1158.
Wahl, T. L. (1998). Predicting Embankment Dam Breach Parameters – A Literature Review and Needs Assessment,
Dam Safety Research Report DSO-98-004, US Bureau of Reclamation, Dam Safety Office, July.
www.tailings.info
Estimation of Tailings Dam Break Discharges
Questions / Comments?